1. Field of Invention
This invention relates to improvements in dental articulators and, in particular to an inspection and calibration system for a dental articulator.
2. Brief Statement of the Prior Art
In the development of dental prostheses such as crowns, bridges, inlays and dentures, the dentist mounts casts of the dental structures in cast relating devices which range from simple, inexpensive devices which reproduce only the opening and closing movements of the jaw to very complex, fully adjustable dental articulators, such as those described in my prior U.S. Pat. Nos. 3,343,264; 3,590,487; and 4,024,640. The articulators disclosed in those patents are arcon type with adjustable guides which allow the articulator to reproduce the movements of the human jaw, e.g., by permitting a controlled degree of lateral, vertical and posterior-anterior translation of the condyles during lateral rotation of the articulator members. The fully adjustable articulators are approximately six to ten times more costly than the simple devices.
Casts of the patient's dental structures are mounted in the articulating devices by mounting plates which are secured to the upper and lower members of the articulator with threaded screw attachments which are cumbersome to use. An attempt has been made to improve the efficiency of mounting casts by use of cast aluminum plates with permanent magnets and steel armatures, however, the magnetic attraction of these plates to the mounting armature is not adjustable and frequently is excessive.
It is a general practice of dentists to leave casts mounted in a dental articulator until completion of the case which, in extensive cases, may take several months. This practice has been referred to as the "one instrument system". During this time, the articulator is used only a matter of hours to replicate the movements of the human jaw during fabrication of the dental occlusion. Typically, the articulator is unavailable for use on other cases for many hours, days and sometimes weeks, particularly in extensive cases, awaiting other stages of the fabrication processes or the patient's healing processes, or completion of other treatments. The consequence is that the dentist must have many articulators; a very costly investment.
The one instrument system in which the case remains in one instrument during the entire fabrication process leads to my inventions disclosed in my U.S. Pat. Nos. 3,750,289 and 3,808,688. In these patents, I describe an inspection means for calibrating the vertical and horizontal adjustments of the articulator.
in 1972, I introduced a two instrument system which used a device for calibrating articulators in both the vertical and horizontal planes and an inspection gauge to align the bows of a family of articulators so that casts could be transferred between the articulators. My objective was to allow the casts to be mounted in simple inexpensive articulators for certain stages of the fabrication process and only mount the casts in fully adjustable articulators for limited periods of time when the fully adjustable capabilities of those articulators were needed. It was the objective of this invention, called a "Two Instrument System", to allow the casts to be transported between work stations independently of the articulator and to use an articulator selected at each work station for the particular work to be done at that point in time. This was intended to reduce the number of articulators a dentist needed by avoiding tying up an expensive articulator for the total time while the restoration was being fabricated. This "Two Instrument System" did not achieve commercial success because it was very difficult and time consuming to align the bows of the articulator. Although I provided an inspection gage for this purpose, difficulties were experienced with this gage which were not entirely overcome. One problem was that the bows were aligned with finger pressure used to slide the upper member of the instrument against the lower member while attempting to align the bows precisely within a tolerance of a thousand of an inch. Frequently, tightening the lock screws would push the instrument out of specification. Furthermore, the prior inspection device described in my U.S. Pat. No. 3,808,688 was inefficient because the dial indicators of that device, which sensed the right and left vertical separations of the bows of the instrument, were responsive to adjustments on both sides of the articulator, whereby the left side indicator would respond to adjustment on the right side of the articulator. This was referred to as "run out" and greatly complicated calibration of the articulator since the dentist or technician was required to go back and forth in repeated adjustments five or six times to achieve a null reading on both sides of the articulator. The result was that few users developed the necessary skill to calibrate an articulator quickly, and the system did not receive broad acceptance.